A New and Unusual Force in the Universe Just Got Even Stranger

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New
research has expanded on the
discovery of a strange phenomenon called blackbody force, showing that
the effect of radiation on particles surrounding massive objects can be
magnified by the space that warps around them. The
find could affect how we model the formation of stars and planets, and even
help us finally detect a theoretical form of
radiation that allows black holes to evaporate.

In 2013,
physicists announced radiation emitted from objects called 'blackbodies' could
not only nudge small particles away, but tug them closer. What's more, for
hot-enough objects with only a small amount of mass, the pushing force could be
stronger than their gravitational pull.

If
you've never come across the term, a blackbody is any opaque object that
absorbs visible light, but doesn't reflect or transmit it. Technically,
blackbodies describe theoretically perfect objects that cannot reflect any
light at all. Physical examples such as the carbon nanotube materials used
to make
the crazy-looking Vantablack coatings come pretty close.

To
understand this effect, it helps to know that atoms can move and change
direction when the photons they absorb cause a shift in their momentum. Given
the right conditions, objects as large as a cell can be nudged around by a beam
of light - a phenomenon commonly used in a form of technology called optical tweezers.

Physicists
have known for about a century that electromagnetic radiation can change the
properties of nearby atoms through the Stark effect, which
changes the positions of its electrons to sit in a lower energy state.

This
happens to make them more likely to move towards towards the brighter parts of
a beam of light. The Austrian researchers put two and two together, showing
how heat radiation could cause light to not only push particles away, but
thanks to the Stark shift, they could also be pulled towards the object.

"The
interplay between these two forces - a typically attractive gradient force
versus repulsive radiation pressure - is routinely considered in quantum optics
laboratories, but it was overlooked that this also shows up with thermal light
sources," lead researcher Matthias Sonnleitner from the University of
Innsbruck told
Phys.org back in 2013.

While
force is incredibly weak, they also showed that the radiation's net pulling
power could actually be greater than the tiny amount of gravity produced by
minuscule, hot objects, having implications for particles smaller than a dust
grain.

"These
sub-micron-sized grains play an important role in the formation of planets and
stars or in astro-chemistry. Apparently, there are some open questions on how
they interact with surrounding hydrogen gas or with each other. Right now, we
are exploring how this additional attractive force affects the dynamics of
atoms and dust." said
Sonnleitner.

Fast-forward
to now, and another team of physicists has taken up where Sonnleitner and his
colleagues left off, exploring the effect of both the blackbody's shape and its
effect on the curvature of surrounding spacetime on this optical attraction and
repulsion. In particular, they calculated the warping of space - or topology -
around a spherical and a cylindrical blackbody, and measured how the
differences might affect the blackbody radiation forces.

They
found the curvature of the spherical blackbody and the topology of space
surrounding it had a magnifying effect on the attractive force due to both the
effect of gravity and the angle at which the radiation struck the particles. This
wasn't the case for the cylinder, with its flat surface and surrounding space,
where the blackbody effect wasn't magnified.

While
the effect wouldn't be detectable in the laboratory, or even for objects the
size of our Sun, for massive blackbody objects like
neutron stars or more exotic forms of space-bending physics, this
effect could make a significant difference.

"We
think that the intensification of the blackbody force due to the ultradense
sources can influence in a detectable way the phenomena associated with them,
such as the emission of very energetic particles, and the formation of
accretion discs around black holes," lead researcher Celio Muniz from
Ceará State University, Brazil, explained
to Phys.org.

The
team also applied the previous findings on the blackbody force to a concept
called a global monopole -
a theoretical point similar to an electric charge, which affects the shape of
surrounding space without gravity - as well as another theoretical warping of
space called a cosmic string.

"This
work puts the blackbody force discovered in 2013 in a wider context, which
involves strong gravitational sources and exotic objects like cosmic strings as
well as the more prosaic ones found in condensed matter," Muniz
said.